package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisConstants;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;

    @Override
    public Result queryById(Long id) {
         //缓存穿透
        // Shop shop = queryWithPassThrough(id);
//        cacheClient.queryWithPassThrough(RedisConstants.CACHE_SHOP_KEY, id, Shop.class, new Function<Long, Shop>() {
//            @Override
//            public Shop apply(Long aLong) {
//                return getById(aLong);
//            }
//        }, RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);

        Shop shop = cacheClient.queryWithPassThrough(RedisConstants.CACHE_SHOP_KEY, id, Shop.class,
                this::getById, RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);

//        //利用互斥锁解决缓存击穿
//         Shop shop = queryWithMutex(id);

                //利用逻辑过期解决缓存击穿
                // Shop shop = queryWithLogicalExpire(id);
                //Shop shop = cacheClient.queryWithLogicalExpire(RedisConstants.CACHE_SHOP_KEY, id, Shop.class,
                //       RedisConstants.LOCK_SHOP_KEY, this::getById, RedisConstants.CACHE_SHOP_TTL, TimeUnit.SECONDS);

        if(shop == null){
            return Result.fail("店铺不存在");
        }

        //返回
        return Result.ok(shop);
    }

    //利用互斥锁解决缓存击穿
    public Shop queryWithMutex(Long id){
        //1.从redis中查询商铺缓存
        String key = RedisConstants.CACHE_SHOP_KEY + id;
        String shopJson = stringRedisTemplate.opsForValue().get(RedisConstants.CACHE_SHOP_KEY + id);

        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在, 直接返回商铺信息
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中的是否是空字符串
        if(shopJson != null){
            return null;
        }

        //实现缓存重建
        //1.获取互斥锁
        String lockKey = null;
        Shop shop = null;
        try {
            lockKey = RedisConstants.LOCK_SHOP_KEY + id;
            boolean isLock = tryLock(lockKey);
            //2.判断是否获取锁成功
            if (!isLock){
                //3.获取失败, 休眠并重试
                Thread.sleep(50);
                queryWithMutex(id);
            }

            //4.获取锁成功,根据id查询数据库
            shop = getById(id);
            //模拟重建的延时
            Thread.sleep(200);
            //5.不存在,返回错误
            if(shop == null){
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(key, "", RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }
            //6.存在,写入redis,返回数据
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop),
                    RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //7.释放锁
            unlock(lockKey);
        }
        return shop;
    }

    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR  = Executors.newFixedThreadPool(10);
    public Shop queryWithLogicalExpire(Long id) {
        //1.从redis中查询商铺缓存
        String key = RedisConstants.CACHE_SHOP_KEY + id;
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.未命中返回空
        if(StrUtil.isBlank(shopJson)){
            return null;
        }

        //3.命中, 先把json字符串反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        Shop shop = JSONUtil.toBean(data, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //4.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //5.未过期, 返回店铺信息
            return shop;
        }

        //6.已过期,需要进行缓存重建
        //6.1 获取互斥锁
        String lockKey = RedisConstants.LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        if(isLock){
            //6.2 获取锁成功 开启独立线程,进行缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    this.saveShop2Redis(id, 20L);
                } catch (Exception e){
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unlock(lockKey);
                }

            });
        }

        //6.3 返回过期的商品信息
        return shop;
    }

    //redis缓存空值解决缓存穿透问题
    public Shop queryWithPassThrough(Long id) {
        //1.从redis中查询商铺缓存
        String key = RedisConstants.CACHE_SHOP_KEY + id;
        String shopJson = stringRedisTemplate.opsForValue().get(RedisConstants.CACHE_SHOP_KEY + id);

        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在, 直接返回商铺信息
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中的是否是空字符串
        if(shopJson != null){
            return null;
        }

        //4.不存在, 查询数据库
        Shop shop = getById(id);

        //5.不存在,返回错误
        if(shop == null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }

        //6.存在,写入redis,返回数据
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop),
                RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);
        return shop;
    }

    //利用逻辑过期时间解决缓存击穿问题
    //缓存预热
    public void saveShop2Redis(Long id, Long expireSeconds) throws InterruptedException {
        Shop shop = getById(id);
        //模拟缓存延迟
        Thread.sleep(200);
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //加入缓存
        stringRedisTemplate.opsForValue().set(RedisConstants.CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if(id == null){
            return Result.fail("店铺id不能为空");
        }

        //1.更新数据库
        updateById(shop);
        //2.删除缓存
        stringRedisTemplate.delete(RedisConstants.CACHE_SHOP_KEY + id);

        return Result.ok();
    }
}
